Claim CD301:

Evaporites can precipitate from unsaturated brines; they can form without
evaporation (H. M. Morris 1974). A mechanism is sketched by J. D. Morris
(2002):

Many now think the salt was extruded in superheated, supersaturated salt
brines from deep in the earth along faults. Once encountering the cold
ocean waters, the hot brines could no longer sustain the high
concentrations of salt, which rapidly precipitated out of solution, free
of impurities and marine organisms.

Response:

Most evaporite deposits are not associated with evidence of
hydrothermal activity. The huge amount of energy needed to deposit
kilometers of salt in a few weeks should have left obvious evidence,
such as heat-altered rocks or evidence of magma. Typical hydrothermal
deposits such as iron and manganese are not often found associated with
evaporites. Sea-floor basalts are a common site of hydrothermal
activity, and other hydrothermal deposits are found there, but salt
deposits are never found associated with them.

Hydrothermal systems operating today are not depositing any salt, much
less the thick, laterally extensive layers we find in the sedimentary
record. In fact, hydrothermal solutions contain less sodium and
chlorine than normal sea water (Open University Team 1989, 100).

Evaporites are observed forming today in basins with no significant
outflow; the water that flows in evaporates and leaves behind layers of
dissolved salts. Ancient evaporites are also found in sedimentary
context, and they are often associated with other evidence of being
open to the air, such as footprints, dessication cracks and occasional
raindrop impressions. None of these structures are consistent with an
underwater hydrothermal environment.

Evaporites are also found in sabkha environments, where crystals or
nodules of salt grow within fine-grained sediments as saline
groundwater (usually from a nearby ocean) is drawn upward by
evaporation. As the water evaporates at the surface, salt nodules
grow, often forming a chicken-wire pattern. Some sabkha evaporites
grow into gypsum rosettes, huge crystals resembling flowers. These
features also are known from ancient evaporites. They also are
inconsistent with hydrothermal deposition.

References:

Open University Team, 1989. The Ocean Basins: Their Structure and
Evolution. Oxford: Pergamon.